The present invention relates generally to a holographic read-only memory, and more particularly to a compact holographic read-only memory that does not need to have any movable parts.
Optical storage systems have a number of distinct advantages over magnetic storage systems. For example, they have higher storage capacity than magnetic storage systems. Also, data access is done optically, without the need for contact.
One approach to access data optically is based on CD-ROMs and DVDs. Even movies are now available in these formats. Unfortunately, they have a number of weaknesses. For example, to access data, disks are typically spun around. The need for moving the disks before data can be accessed reduces data-access speed, and increases power consumption.
Another approach is based on holographic optical disks. They offer much higher storage capacity than the compact discs. However, again they have to rely on moving or spinning the disks, reducing data-access speed and increasing power consumption.
A third option is based on optical RAMs, as discussed in U.S. Pat. No. 5,696,714. An optical RAM is a non-holographic optical memory, with an array of imaging optics integrated on top of a storage medium. Fabricating such integrated optical devices, with imaging optics on top of a storage medium, can be both difficult and expensive.
It should be apparent from the foregoing that there is still a need for an apparatus and method to access information optically, with higher storage capacity than compact disks, lower power consumption than existing optical disks, and simpler manufacturing processes than optical RAMs.